Great Expectations, Small-Screen Letdowns : Television: When is a hit not a hit? When a TV series is spun off a box-office blockbuster. Too often the show can't compete with a big-screen cousin.

For years, producer Brian Grazer resisted offers to adapt his film hits such as "Splash" and "My Girl" for television, insisting that a movie needed a broad, open-ended theme to lend itself to a weekly series. But with his and Ron Howard's 1989 "Parenthood," the heretofore cautious Grazer thought he had the ideal candidate.

After all, "Parenthood" was a character-driven movie dealing with "the daily problems of existing," as Grazer saw it. "It could just as easily have been a series as a movie."

It could have. But "Parenthood" the movie grossed nearly $100 million at the box office. "Parenthood" the series survived just 12 episodes on NBC in 1990, leaving Grazer and Howard to ponder just what went wrong.

"Parenthood" wasn't alone. Recent attempts at converting big-screen wonders into television series have been uniformly unsuccessful. "A League of Their Own" lasted just a few weeks on CBS last spring. Remember "Baby Talk," the ABC series based on the $140-million grossing film "Look Who's Talking"? How about the 1990 television versions of "Ferris Bueller's Day Off," "Working Girl" or "Uncle Buck"? That's OK. No one else does either.

There have been exceptions over the years, among them "MASH," "Alice" and CBS' current "In the Heat of the Night," based on the 1967 Academy Award-winning film starring Rod Steiger and Sidney Poitier. But to say that most film-inspired series have failed to take mainstream TV by storm is an understatement.

Indeed, out of 38 new series this season, none is based on a movie--ironic at a time when a record number of television shows are finding a profitable afterlife as feature films, from "Star Trek" to "The Addams Family" to "The Fugitive," with "The Beverly Hillbillies" and "The Flintstones" in the wings.

The biggest reason for their absence is likely the most obvious: the abysmal track record of such adaptations.

"If you see so many failures and so few successes, you've got to think long and hard about bringing (movie-based series) to television," says Betsy Frank, senior vice president at the Saatchi and Saatchi advertising agency in New York. "They should work because (they're) a pre-sold concept. They don't work because nine times out of 10 you've recast the roles and the viewers are unhappy."

According to Bob Greenblatt, senior vice president of drama development at the Fox network, the pressures of trying to compete with and mirror the movies are almost too great to bear.

"It's really easy to fail in trying to re-create what a movie had, because you never really can," he said.

If developing a big-name movie like "A League of Their Own" for television affords networks built-in name recognition and free advertising, it is precisely the heightened level of audience expectation that often proves insurmountable for the series.

"There is no doubt that the name 'Indiana Jones' was a double-edged sword," recalls George Lucas about his ill-fated 1992 series "The Young Indiana Jones Chronicles." "On the one hand, it helped to get the series on the air, but, on the other hand, the name automatically brought expectations of an action series."

Even though critics and network executives like Greenblatt lauded Lucas for not trying to re-create his movie on the small screen, viewers demanded more.

"It didn't matter how many times I said it was a coming-of-age series about a young boy's exploration of history; people still expected to see that rolling boulder (from "Raiders of the Lost Ark")," Lucas explained.

While Lucas never intended his series to be a direct spinoff, others who have tried and failed felt trapped by the process: Viewers can't help but expect more of what drew them to the movie in the first place, yet television can't always deliver that.

"Television is a different mission to me than movies," said Lawrence Gay, a supervising producer on NBC's short-lived 1990 series "Ferris Bueller." "There's no way you could do in television what (director) John Hughes did with the feature. It was Ferris Bueller's day off. . . . With the show, you have to come back every week ."

That TV series usually do not feature the same big-name stars is yet another area where viewers can feel let down; even well-known TV performers such as Ed Begley Jr. ("Parenthood") and Kate Jackson ("Baby Boom") couldn't duplicate the memorable movie performances of Steve Martin and Diane Keaton.

This problem has been accentuated by the increasing speed at which theatrical releases make their way to home video and cable TV and by the growing tendency of studios to order sequels to their most successful films.

"We can watch (the original actors) on cable in our homes over and over again. It is difficult to re-establish those roles with the public," said Dennis Gallegos, who was producing "Baby Talk" for ABC in 1991 at the same time the sequel "Look Who's Talking Too" was in production.